Not applicable.
The present invention generally relates to highway snow and ice control and more particularly to the production of brine therefor.
Highway snow and ice control frequently is carried out by governmental authorities with the use of dump trucks, which are seasonally modified by the addition of snow-ice treatment components. Operating systems employed for these snow and ice control implements have been substantially improved over the past decade. An initial such improvement has been achieved through the utilization of microprocessor driven controls over the hydraulics employed with the seasonally modified dump trucks. See, for example, U.S. Pat. Nos. Re 33,835 and 5,318,226. This latter approach, for example, sometimes is referred to as a xe2x80x9czero-velocityxe2x80x9d method for salt distribution.
Investigations into techniques for controlling snow-ice pavement envelopment have recognized the importance of salt in the form of salt brine in breaking the bond between ice and the underlying pavement. Without a disruption of that bond, little improvement to highway traction will be achieved. For example, the plow merely will scrape off the snow and ice to the extent possible, only to leave a slippery coating which may be more dangerous to the motorist than the pre-plowed road condition.
When salt has been simply broadcast over an ice-laden pavement from a typical spinner, it will have failed to form a brine of sufficient salt concentration to break the ice-pavement bond. The result usually is an ice coated pavement, in turn, coated with a highly dilute brine solution developed by too little salt, which will have melted an insufficient amount of ice for traction purposes. This condition is encountered often where granular salt material contains a substantial amount of xe2x80x9cfinesxe2x80x9d. Fines are very small salt particles typically generated in the course of transporting, stacking, and storing road maintenance salt in dome-shaped warehouses and the like.
Road snow-ice control studies have revealed that the activity of ice melting serving to break the noted ice-pavement bond is one of creating a saltwater brine of adequate concentration. In general, an adequate salt concentration using conventional dispersion methods requires the distribution of unacceptable quantities of salt on the pavement. Some investigators have employed saturated brine as the normal treatment modality by simply pouring it on the ice covered highway surface from a lateral nozzle-containing spray bar mounted behind a truck. A result has been that the thus-deposited brine concentration essentially immediately dilutes to ineffectiveness at the ice surface, with a resultant dangerous liquid-coated ice highway condition.
Attempting to remove ice from pavement by dissolving the entire amount present over the entire expanse of pavement to be treated is considered not to be acceptable from an economical standpoint. For example, a one mile, 12 foot wide highway lane with a xc2xc inch thickness of ice over it should require approximately four tons of salt material to make a 10% brine solution and create bare pavement at 20xc2x0 F. Technical considerations for developing a salt brine effective to achieve adequate ice control are described, for example, by D. W. Kaufman in xe2x80x9cSodium Chloride: The Production and Properties of Salt and Brinexe2x80x9d, Monograph Series 145 (Amer. Chem. Soc. 1960).
The spreading of a combination of liquid salt brine and granular salt has been considered advantageous. In this regard, the granular salt may function to maintain a desired concentration of brine for attacking the ice-pavement bond and salt fines are more controlled by dissolution in the mix. The problem of excessive salt requirements remains, however, as well as difficulties in mixing highly corrosive brine with particulate salt. Typically, nozzle injection of the brine is the procedure employed. However, attempts have been made to achieve the mix by resorting to the simple expedient of adding concentrated brine over the salt load in a dump bed. This approach is effective to an extent. However, as the brine passes through the granular salt material, it dissolves the granular salt such that the salt will not remain in solution and will recrystallize, causing bridging phenomena and the like inhibiting its movement into a distribution auger.
A practical technique for generating a brine of sufficient concentration to break the ice-pavement bond is described in U.S. Pat. No. 5,988,535. With this technique, ejectors are employed to deposit a salt-brine mixture upon a highway as a relatively narrow, continuous and compact band of material. To achieve such narrow band material deposition at practical highway speeds of 40 mph or more, the salt-brine mixture is propelled from the treatment vehicle at a velocity commensurate with that of the vehicle itself and in a direction opposite that of the vehicle. Further, the material is downwardly directed at an acute angle with respect to the plane defined by the pavement. When the salt-brine narrow band is deposited at the super-elevated side of a highway lane, the resultant concentrated brine from the band is observed to gravitationally migrate toward the opposite or downhill side of the treated lane to provide expanded ice clearance. The result is a highly effective snow-ice treatment procedure with an efficient utilization of salt materials. Because the lanes of modem highways are super-elevated in both a right and a left sense, two spaced apart salt ejectors are employed to deposit the narrow band concentration at positions corresponding with the tire tracks of vehicles located at the higher or elevated portion of a pavement lane. A feature of the apparatus of this system is its capability for being mounted and demounted upon the dump bed of a conventional highway maintenance truck in a relatively short interval of time. As a consequence, these dump trucks are readily available for carrying out tasks not involving snow-ice control. Additionally, the apparatus is configured such that the dump beds remain in a lowered or down position throughout their use, thus improving the safety aspect of their employment during inclement winter weather.
Regardless of the snow/ice control technique chosen, the brine still must be manufactured. The manufacture of brine at a central station remains the practical technique of choice for most governmental highway organizations. Practical problems exist, however, in this regard since the brining forming operation should be kept indoors to prevent lines from freezing and for worker safety and comfort. Operation of a front-end loader to move the piles of salt crystals necessary for such brine forming operation, however, can be dangerous if practiced indoors. Then, too, the final brine need not be kept inside, as it needs to be loaded onto the salt-spreader trucks. It is to such operations that the present invention is addressed.
An system for making brine for use, for example, by state highway departments to de-ice roads is disclosed. The system employs an outdoor hopper into which a front-end loader can load salt (e.g, NaCl crystals or pellets). Located indoors is a sump tank. Tap water and make-up (recycle) brine from the sump tank is pumped from indoors to the outdoor mixing tank to make fresh brine. Brine from the outdoor mixing tank flows back into the sump tank. Located inside the sump tank is a plastic jug filled with the 23.3% NaCl eutectic brine that is desired to be made from the salt in the outdoor hopper. The flows to and from the outdoors mixing tank and indoor sump tank continue until the correct concentration of brine is present in the indoor sump tank. As soon as the sump tank has the correct concentration of brine in it, the plastic jug is buoyed (match in density), which automatically activates a switch that permits the brine in the mix tank to be pumped to the brine storage tank(s) for loading into trucks for dispensing onto highways.
The salt brine manufacturing system for implementing the salt brine method includes a mixing tank connected to a source of tap water and to a source of dilute brine. A sump tank for supplying dilute brine to the mixing tank is fitted with a brine product sensor for determining whether the brine therein has a desired concentration of salt to make a brine product. A recirculation pump for passing the source of tap water and the dilute brine from the sump tank to the mixing tank is provided. A storage tank is provided. Finally, a pump is provided for passing a brine product from the mixing tank to the storage tank.
Advantages of the present invention include a worker safety manufacturing operation for the preparation of salt brine. Another advantage is a simple, yet reliable technique for the preparation of salt brine. A further advantage is the ability to make a salt brine of desired precise salt concentration. These and other advantages will be readily apparent to those skilled in the art based on the disclosure set forth herein.